Abstract:

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A uniform model, in which the crack, V-notch, U-notch and arc are described as breach
uniformly, is put forward in this paper. The tip radius, depth and field angle of breach are regarded as
the parameter of annularly breached bar. The stress field and displacement field near the tip of the
annularly breached bar under bending, in which takes fα(a/b) as its descriptive parameter, was given.
All forms of breaches according to the change of tip radius, depth and field angle were discussed. The
effects of parameters on fα(a/b) in bending were analyzed. The criteria for the safety design and
fracture design both of which on fα(a/b) were obtained. The results not only can be applied widely to
anti-fracture design but also be used for reference in anti-fatigued design in product lifecycle
management.

Abstract: The viscosity of material is considered at propagating crack-tip. Under the assumption
that the artificial viscosity coefficient is in inverse proportion to the power law of the plastic strain
rate, an elastic-viscoplastic asymptotic analysis is carried out for moving crack-tip fields in
power-hardening materials under plane-strain condition. A continuous solution is obtained
containing no discontinuities. The variations of the numerical solution are discussed for mode I
crack according to each parameter. It is shown that stress and strain both possess exponential
singularity. The elasticity, plasticity and viscosity of material at the crack-tip only can be matched
reasonably under linear-hardening condition. The tip field contains no elastic unloading zone for
mode I crack.

Abstract: Basing on the theoretical study on the stress intensity factor (SIF) of the crack inclined across the interface of the cermet cladding part, the finite element analysis (FEA) of the crack’s SIF is made. The change laws of the SIF with the load action angle , the load Q, the clad thickness ratio h1/h, the elastic modulus ratio E1/E2, the inclined angle of the crack β1, and the crack length ratio a1/a2 are obtained. The research results have theoretical and steering significance on the wide application of the cermet cladding part.

Abstract: The wedge splitting (WS) test is now a promising method to perform stable fracture mechanics tests on concrete-like quasi brittle materials. Fracture parameters, such as fracture toughness and critical crack opening displacement and et.al, are however not easy to determined since formulae available from stress intensity factor manual are restricted to standard specimen geometry. The paper attempts to compute expressions for commonly used fracture parameters for a general wedge splitting specimen. By means of finite element analysis program, test simulation was performed on non-standard wedge splitting specimen with different depth and initiation crack length, and thereafter expressions were proposed for stress intensity factor at the pre-cast tip and crack mouth opening displacement on the load line. Based on the work above, size effect on the unstable fracture toughness and crack extension were investigated, and the consistency of fracture toughness data for various specimen depth as well as initiation crack length is demonstrated. The crack extension is little sensitive to the initiation crack length, it increases with the depth of specimen, which can be explained by the boundary influence of the specimen.

Abstract: FEM linear numerical analysis of stress distribution demonstrated that the model Zappalorto and Lazzarin for analysed V-hole ended notch, relatively correctly predicts the stress distribution at the tip of the notch, especially for small angles of opening. The maximum levels of hoop stress and a tangential for load Mode II strongly dependent on the radius of the notch. The stress reaches its maximum value at a certain distance from the tip of the notch, approximately equal to half of the hole circle radius. The most effective way to reduce the levels of maximum stress at the notch is to increase the radius. When changing radius of 0.5 mm to 2 mm can reduce the degree of stress concentration approx. 40%.